The goblins are frankly weak. I'm not scared if I see one in a cave. Either a Psijjic, an Imperial battlemage, A tongue, one trained in Pankratosword, or a Necromancer. Any one of those skilled enough with their art would be capable of destroying much of the world over.
I'm not sure if anyone is still trained in the Pankrat, but the remaining Ansei would be pretty beast. Psijics would be tough to deal with as well, due to their incredible flexibility with magic (meaning they can use something akin to mysticism to produce just about any spell imagineable). I'm not as familiar with Tongues, though I know their power is also rather dynamic. With Necromancers it would really depend on what quality we are talking about, is this a run of the mill grave robber or a serious upper level servant of Mannimarco?
Anyway, I voted for DB assassin, though in a head to head fight they might lose against more heavily armored foes. As was said earlier, it is just like with the Ninja vs. Spartan in the show- assassins wouldn't get into a one on one fight with an Ordinator. That's why they're so dangerous, not because of their skill with a blade or bow, but because of their stealth. And when their target is expecting it it really isn't fair anymore.
The Hands of Almalexia are pretty awesome as well, though they rank with Psijics and Ansei in the overpowered category. So my second pick would probably be either Ordinator or Blade, due to their combat skill and training.